Question category: Endocrinology
A 37 year old male presents due to loss of libido and erectile dysfunction. He has also noticed a small lump in his testes. On further questioning he has been suffering from headaches and tiredness over the last few months. Bloods reveal a low testosterone level and GnRH levels are also low. There is a mild elevation of prolactin. There is evidence of an elevated IGF1 levels. Which of the following is the most likely diagnosis?